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Exercising Toward Repair of the Spinal Cord

When Christopher Reeve went on national television last week to announce that he could wiggle his fingers and hips, the news seemed startling. Paralyzed from the neck down after a horseback riding accident in 1995, Mr. Reeve had been told repeatedly that he would never be able to move any part of his body below his shoulders.

But scientists who study the brain say Mr. Reeve's recovery is part of a quiet revolution in how intense physical exercise can help restore the brain and spinal cord after serious injury.

At academic research centers in the United States, Europe and Japan, paralyzed patients are hanging from harnesses, walking on treadmills and tying down limbs to force the use of paralyzed arms and legs. Some are being fit into robots designed to help move their bodies. Using such techniques, an estimated 500 paraplegics who had limited sensations in their lower bodies are now able to walk for short distances, unassisted or using walkers, scientists say.

The limits of what physical exercise can do for paralyzed patients is not known. While each person and each injury is unique, and some people recover spontaneously, an estimated 200,000 Americans are living with spinal cord injuries that have not improved, according to the National Spinal Cord Injury Statistical Center at the University of Alabama at Birmingham. Which therapy or combination of therapies will work for each person -- including the use of experimental drugs and stem cells -- is also not known.

However, the ordinary repetitive motions used in most rehabilitation centers, like squeezing a ball, are almost certainly not enough to revive badly injured adult brains and spinal cords, scientists say. Indeed, patients are usually told that after one year, two at the most, they will never make further progress in their abilities to move or feel sensation.

Mr. Reeve, the actor and director, was totally paralyzed for five years after his accident but stuck to an exercise regime because, he says, it kept his muscles strong and his mood elevated. Then one morning two years ago, he found that he could lift his left index finger on his own.

Thinking back on that day, he said: ''My first reaction was to curb my enthusiasm. But inside, my hope and belief was that if my finger could suddenly move on command, I had to explore every other part of my body to see what was possible.''

While still dependent on a wheelchair and respirator, Mr. Reeve, who will turn 50 on Wednesday, has recovered the ability to move all fingers on both hands, move each of his joints while floating in water and from a supine position push hard against a therapist's chest with each of his legs. This does not mean he can walk -- for one thing, he cannot support his upper body -- but he has regained enough muscle strength to carry out a pushing motion.

''Chris Reeve has called into question every assumption about the capacity of the human brain and spinal cord to recover after catastrophic injury,'' said Dr. Michael Merzenich, a pioneer in neuroplasticity research at the University of California San Francisco School of Medicine. ''He has shown that intense exercise is not only good for the healthy nervous system, it can bring body and brain back from the oblivion of paralysis.''

But the activity has to be specially designed to engage a mature nervous system, Dr. Merzenich said. The experience needs to be relevant and to have many components. It has to be broken down into very small steps and then pounded into the patient's body. Such therapy may have to go on for years before it will have an effect, he said. Because these therapies are still largely experimental, Medicare and most insurance companies will not cover their costs, which tend to be much higher than costs for conventional physical therapy. The weeks or months of rehabilitation typically paid for by insurance companies are rarely enough, scientists say.

These new ideas about adult plasticity have been slow to catch on because people are discouraged by what they see around them, said Dr. Bruce Dobkin, a rehabilitation expert at the University of California in Los Angeles. The fact is that most stroke and spinal cord patients reach a plateau after several months, he said. They are told to go home and live with their permanent disability.

The idea that the adult nervous system is set in stone began to change more than 20 years ago, said Dr. John W. McDonald, an assistant professor of neurology at the Washington University School of Medicine in St. Louis who is also Mr. Reeve's doctor. The synapses that help carry signals inside the brain turn over or renew themselves -- a person gets entirely new ones -- several times in adulthood, Dr. McDonald said. This means the adult brain is capable not only of learning but of repairing itself if challenged with the right kind of activity.

The brains of infants and children build all their complex circuitry in response to activity, Dr. McDonald said. This natural plasticity slows way down in adulthood but does not turn off. One way to drive plasticity in the adult brain is to break what has to be learned into smaller steps.

Adult Japanese speakers can easily be taught to hear and pronounce L's and R's -- sounds that they cannot usually distinguish -- if the sounds are stretched out by a computer. The activity also must matter to the individual, Dr. Merzenich said. If it is boring and mindless, the brain's plasticity mechanisms will not kick in. When a person focuses and pays attention, brain molecules turn on the reward circuitry that promotes plasticity.

These strategies for enhancing adult brain plasticity apply to damaged brains as well as to healthy ones. At research centers, including one at the University of Alabama in Birmingham, some stroke patients are making unexpected progress when their good arms are tied down and they are forced to use their bad arms for everyday tasks. The activity literally rewires damaged areas of their brains.

In spinal cord rehabilitation, patients in Los Angeles, Miami and Zurich are suspended in harnesses while their feet are put through walking movements on treadmills. Doctors at the University of California are building robots to help paralyzed patients practice walking.

Many spinal cord injuries leave some ascending and descending nerve tracts alive but stunned, Dr. McDonald said. Without activity, these fibers atrophy and the person ends up in a wheelchair. But when muscles are stimulated with electrodes and exercise, the nerve tracts sometimes partly revive.

Mr. Reeve is challenging the accepted limits of all such therapies based on exercise and plasticity. First, his injuries are more severe. Most patients who get on treadmills or tie down limbs have some spared movement and can breathe on their own. Second, he refuses to give up.

In a recent telephone interview, Mr. Reeve recalled his efforts to reawaken his body. After the accident he used electrical current to maintain his muscle mass and increase circulation. He lay on a table that tilted him vertically to increase bone density and enhance circulation. He hung in a harness over a treadmill. In 1999 he began an intense exercise program on a recumbent bicycle in which his muscles were electrically stimulated to move the pedals an hour at a time.

After a year on the bike, he could move a finger. ''That's when I decided to exercise even more intensely,'' he said. ''What I think happened, by exercising over such a long period of time, is that perhaps dormant pathways have been reawakened.''

Mr. Reeve said brain scans show that 70 percent of his body is now actively represented in his brain, meaning sensory information is flowing into his cortex from the periphery. A study confirming this is to be published in the Journal of Neuroscience. Some motor functions also appear to be coming back. By artificially raising levels of carbon dioxide in his blood via his respirator, he is forcing nerves in his brain stem to reflexively move muscles in his diaphragm -- thus retraining his body to breathe on its own. The high level of carbon dioxide tells the brain it is suffocating and triggers the breathing reflex.

It may take many years of intense exercise to produce these effects, Mr. Reeve said. To people who must use wheelchairs, he gave this advice: ''Do not give up. Go back to exercise. Even if not much happens right away, you've got to believe. Nothing is impossible.''